RRC ID 6716
Author Shimada N, Maruo T, Maeda M, Urushihara H, Kawata T.
Title Evidence that the Dictyostelium STAT protein Dd-STATa plays a role in the differentiation of inner basal disc cells and identification of a promoter element essential for expression in these cells.
Journal Differentiation
Abstract Dd-STATa, a Dictyostelium homolog of the metazoan STAT (signal transducers and activators of transcription) proteins, is necessary in the slug for correct entry into culmination. Dd-STATa-null mutant fails to culminate and its phenotype correlates with the loss of a funnel-shaped core region, the pstAB core region, which expresses both the ecmA and ecmB genes. To understand how the differentiation of pstAB core cells is regulated, we identified an EST that is expressed in the core cells of normal slugs but down-regulated in the Dd-STATa-null mutant. This EST, SSK348, encodes a close homolog of the Dictyostelium acetyl-CoA synthetase (ACS). A promoter fragment of the cognate gene, aslA (acetyl-CoA synthetase-like A), was fused to a lacZ reporter and the expression pattern determined. As expected from the behavior of the endogenous aslA gene, the aslA::lacZ fusion gene is not expressed in Dd-STATa-null slugs. In parental cells, the aslA promoter is first activated in the funnel-shaped core cells located at the slug anterior, the "pstAB core." During culmination, the pstAB core cells move down, through the prespore cells, to form the inner part of the basal disc. As the spore mass climbs the stalk, the aslA gene comes to be expressed in cells of the upper and lower cups, structures that cradle the spore head. Deletion and point mutation analyses of the promoter identified an AT-rich sequence that is necessary for expression in the pstAB core. This acts in combination with repressor regions that prevent ectopic aslA expression in the pre-stalk regions of slugs and the stalks of culminants. Thus, this study confirms that Dd-STATa is necessary for the differentiation of pstAB core cells, by showing that it is needed for the activation of the aslA gene. It also identifies aslA promoter elements that are likely to be regulated, directly or indirectly, by Dd-STATa.
Volume 73(1)
Pages 50-60
Published 2005-2
DOI 10.1111/j.1432-0436.2005.07301001.x
PII S0301-4681(09)60324-8
PMID 15733068
MeSH Amino Acid Sequence Animals Base Sequence Cell Differentiation / genetics* Coenzyme A Ligases / genetics Dictyostelium / cytology* Dictyostelium / genetics Dictyostelium / growth & development Gene Expression Regulation Molecular Sequence Data Mutation Promoter Regions, Genetic* Protozoan Proteins / genetics* Protozoan Proteins / metabolism Regulatory Sequences, Nucleic Acid STAT Transcription Factors Sequence Homology, Amino Acid Trans-Activators / genetics* Trans-Activators / metabolism
IF 2.688
Times Cited 15
Cellular slime molds G02379